This invention relates generally to a time-correcting mechanism for an electronic timepiece and more particularly to a time-correcting mechanism for a digital electronic timepiece in which an externally actuated rotary switch is used to drive the time-correcting mechanism as in an analog timepiece. Conventionally, in a digital timepiece, a pushbutton is used for providing time-correction inputs, and an internal time-correcting mechanism is operated from the pushbutton. When the time setting of an analog timepiece is corrected, the hands move with the motion of the external stem so that the user can sense a cooperation between the stem which he rotates and the hands on the face of the dial. As a result, watch owners who are accustomed to correcting the time for an analog watch are unfamiliar and uncomfortable with the pushbutton mode of correction provided in the digital timepiece.
A digital timepiece using a rotary switch as the input member for a time-correcting mechanism is already known. However, the quick-feeding frequency of pulses applied to drive the visual display for adjustment must be maintained low so that time advancement is sensed gradationally, that is, in visible increments corresponding with the rotary speed of the rotated external member. As a result, the rotation rate of the switch is only practical in providing for a small incremental correction. On the other hand, to achieve a high feeding rate of the display for large magnitude adjustments, the frequency which is used to drive the display must be high so that the adjustment is accomplished in a reasonable time. Such a high frequency causes the display to appear to jump from time to time rather than to change gradationally.
For example, assume a one-minute counter and assume that a 32-minute correction is required. Also assume that the time required or allowed for the correction is 0.25 seconds in view of the time needed for a person to rotate the external switch. If the correction is to be made in 0.25 seconds, time-correcting quick-feeding clock pulses must be fed to the display at a rate of 32/0.25=128 Hz. However, when the one-minute display is changed at a rate of 128 Hz, it is not visible to the eye that the minute display is changing gradationally, that is, in steps. Moreover, in order to control the application of 32 clock pulses, the circuit will require a large increase in the number of gates and other circuit elements.
What is needed is a time-correcting mechanism for a completely electronic digital timepiece which is operated by an external rotary switch or stem and which provides correction rates which are proportional to the rates applied in rotating the external member.